Apparatus and method for making flexible waveguide substrates for use with light based touch screens

ABSTRACT

Flexible optical waveguide substrates that can be used with touch screen displays. The waveguide substrates include a flexible base material. A first optical layer having a first index of refraction value is formed on the flexible base material. A second optical layer is then formed on the first optical layer, the second optical layer being patterned to form a plurality of optical elements and waveguides respectively. The second optical layer also has a second index of refraction value higher than the first index of refraction value. Lastly, a third optical layer is formed on the second optical layer. The third optical layer has a third index of refraction value lower than the second index of refraction value. The high N second layer is therefore sandwiched between the lower N first and third layers, creating an internally reflective surface wherever the high N and low N materials are in contact. The base material and first, second and third optical layers thus form a flexible waveguide substrate.

RELATED APPLICATIONS

This patent application claims the benefit of Provisional PatentApplication Ser. No.: 60/584,947, filed Jun. 30, 2004, which isincorporated herein by reference for all purposes. This application isalso a continuation-in-part of U.S. application Ser. No. 10/923,550,entitled “Apparatus and Method for a Folded Optical Element Waveguidefor Use with Light Based Touch Screens”, (which claims the benefit ofProvisional Patent Application Ser. No.: 60/584,728, filed Jun. 30,2004), filed on Aug. 20, 2004, in the name of Gerard D. Smits, assignedto the assignee of the present invention, and incorporated in itsentirety herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally light based to touch screendisplays, and more particularly, to an apparatus and method for makingan optical element waveguide that can be used with touch screendisplays.

2. Description of the Related Art

User input devices for data processing systems can take many forms. Twotypes of relevance are touch screens and pen-based screens. With eithera touch screen or a pen-based screen, a user may input data by touchingthe display screen with either a finger or an input device such as astylus or pen.

One conventional approach for providing a touch or pen-based inputsystem is to overlay a resistive or capacitive film over the displayscreen. This approach has a number of problems. Foremost, the filmcauses the display to appear dim and obscures viewing of the underlyingdisplay. To compensate, the intensity of the display screen is oftenincreased. However, in the case of most portable devices, such as cellphones, personal digital assistants, and laptop computers, highintensity screens are usually not provided. If they are provided, theadded intensity requires additional power, reducing the life of thebattery of the device. The films are also easily damaged. These filmsare therefore not ideal for use with pen or stylus input devices. Themotion of the pen or stylus may damage or tear the thin film. This isparticularly true in situations where the user is writing with asignificant amount of force. In addition, the cost of the film scalesdramatically with the size of the screen. With large screens, the costis typically prohibitive.

Another approach to providing touch or pen-based input systems is to usean array of source Light Emitting Diodes (LEDs) along two adjacent X-Ysides of an input display and a reciprocal array of correspondingphotodiodes along the opposite two adjacent X-Y sides of the inputdisplay. Each LED generates a light beam directed to the reciprocalphotodiode. When the user touches the display, with either a finger orpen, the interruptions in the light beams are detected by thecorresponding X and Y photodiodes on the opposite side of the display.The data input is thus determined by calculating the coordinates of theinterruptions as detected by the X and Y photodiodes. This type of datainput display, however, also has a number of problems. A large number ofLEDs and photodiodes are required for a typical data input display. Theposition of the LEDs and the reciprocal photodiodes also need to bealigned. The relatively large number of LEDs and photodiodes, and theneed for precise alignment, make such displays complex, expensive, anddifficult to manufacture.

Yet another approach involves the use of polymer waveguides to bothgenerate and receive beams of light from a single light source to asingle array detector. These systems tend to be complicated andexpensive and require alignment between the transmit and receivewaveguides and the optical elements and the waveguides. The waveguidesare usually made using a lithographic process that can be expensive ordifficult to source. In addition, the waveguides are typically flat. Asa consequence, the bezel around the display is relatively wide. See forexample U.S. Pat. No. 5,914,709.

Accordingly, there is a need for an apparatus and method for makinginexpensive, flexible optical waveguides that can be used with touchscreen displays.

SUMMARY OF THE INVENTION

The present invention relates to an apparatus and method for makinginexpensive, flexible optical waveguides that can be used with touchscreen displays. The apparatus includes a flexible base material. Afirst optical layer having a first index of refraction value is formedon the flexible base material. A second optical layer is then formed onthe first optical layer, the second optical layer being patterned toform a plurality of optical elements and waveguides respectively. Thesecond optical layer also has a second index of refraction value higherthan the first index of refraction value. Lastly, a third optical layeris formed on the second optical layer. The third optical layer has athird index of refraction value lower than the second index ofrefraction value. The high N second layer is therefore sandwichedbetween the lower N first and third layers, creating an internallyreflective surface wherever the high N and low N materials are incontact. The base material and first, second and third optical layersthus form a flexible waveguide substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with further advantages thereof, may best beunderstood by reference to the following description taken inconjunction with the accompanying drawings in which:

FIG. 1 is a touch screen display device.

FIG. 2A is a sheet including a plurality of flexible waveguidesubstrates fabricated thereon according to one embodiment of the presentinvention.

FIG. 2B illustrates a flexible waveguide substrate cut from the sheet ofFIG. 2A.

FIG. 2C is a perspective view of the flexible waveguide substrate cutfrom the sheet of FIG. 2A.

FIG. 2D is a perspective view of the application of the flexiblewaveguide substrate around a touch screen display.

FIG. 3A is a perspective view of another flexible substrate according toanother embodiment of the invention.

FIG. 3B is a diagram illustrating the flexible substrate of FIG. 3A usedaround a touch screen according to the present invention.

FIG. 3C is a diagram illustrating the improved resolution of thesubstrate of FIG. 3A.

FIG. 4A-4C are diagrams of a folded waveguide substrate according to thepresent invention.

FIG. 5 is a flow diagram illustrating the manufacturing steps forfabricating the waveguide substrates of the present invention.

FIG. 6 is a diagram illustrating the manufacture of waveguide substratesaccording to another embodiment of the invention.

FIGS. 7A and 7B are diagrams illustrating another folded waveguideaccording to the present invention.

In the figures, like reference numbers refer to like components andelements.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a touch screen data input device according to oneembodiment of the invention is shown. The data input device 10 defines acontinuous sheet or “lamina” 12 of light in the free space adjacent atouch screen 14. The lamina 12 of light is created by X and Y inputlight sources 16 and 18 respectively. An optical position detectiondevice 20, optically coupled to the lamina 12 of light, is provided todetect data entries to the input device by determining the location ofinterrupts in the lamina 12 caused when data is entered to the inputdevice. The optical position detection device 20 includes an X receivearray 22, a Y receive array 24, and a processor 26. The X and Y inputlight sources 16 and 18 and the X and Y receive arrays 22 and 24 areformed by a single waveguide substrate 28 that surrounds the lamina 12and the touch screen 14.

During operation, a user makes a data entry to the device 10 by touchingthe screen 14 using an input device, such as a pen, stylus or finger.During the act of touching the screen with the input device, the lamina12 of light in the free space adjacent the screen is interrupted. The Xreceive array 22 and Y receive array 24 of the optical positiondetection device 20 detect the interrupt. Based on the X and Ycoordinates of the interrupt, the processor 26 determines the data entryto the device 10. For more information on the data entry device 10, seeco-pending, U.S. application Ser. No. 10/817,564, entitled Apparatus andMethod for a Data Input Device Using a Light Lamina Screen and anOptical Position Digitizer, filed Apr. 1, 2004, and incorporated byreference herein for all purposes.

Referring to FIG. 2A, a sheet 30 including a plurality of flexiblewaveguide substrates 28 fabricated thereon is shown. According to oneembodiment, a plurality of waveguides 28 are fabricated on a singlesheet 30. The individual substrates 28 are fabricated side-by-side inlong, thin, strips on the surface of the sheet 30. After the substrates28 are fabricated, the sheet 30 is cut, singulating the individualwaveguide substrates 28. The sheet 30 can be cut using any one of avariety of well known techniques, for example using a knife, saw blade,etc. Details of the fabrication of the waveguides 28 on the sheet 30 areprovided below.

Referring to FIG. 2B, a flexible waveguide substrate 28 cut from thesheet 28 is shown. As is evident in the figure, the waveguide substrate28 includes a plurality of optical elements 32 provided on one side ofthe substrate 28. According to various embodiments, the optical elements32 may include lenses, diffraction gratings, filters, bragg gratings,coupling horns, etc. A waveguide 34 is optically coupled to each opticalelement 32. The plurality waveguides 34 are grouped together and run inparallel along the length of the substrate 28 in what is sometimesreferred to as a waveguide highway 36.

FIG. 2C is a perspective view of the flexible waveguide substrate 28. Inthis figure, the optical elements 32 are shown along one side of thesubstrate 28. The individual waveguides 34, optically coupled to theoptical elements 32, are shown in grouped together along the opticalhighway 36. The individual waveguides 34 run the length of the substrate28 (not shown in the figure).

Referring to FIG. 2D, a perspective view of the waveguide substrate 28around a touch screen display 14 of input device 10 is shown. Oneapplication of the flexible waveguide substrates 28 is that they canreadily be used to provide the X and Y input light sources 16, 18 andthe X and Y receive arrays 22, 24 for the input device 10. As is shownin the figure, the waveguide substrate 28 is provided around theperimeter of the touch screen 14, with the optical elements 32configured facing inward. Consequently, the optical elements 32 on the Xand Y input light sides of the touch screen are used to create thelamina 12 of light above the touch screen 14. For the sake ofsimplicity, the individual waveguides 34 are not shown in the figure.Alternatively, the optical elements 32 on the X and Y receive sides ofthe display 14 are used to decipher data inputs by detecting interruptsin the lamina 12. A light source 38 provides light to the waveguides 34coupled to the optical elements 32 along the light input sides of thetouch screen 14. An imaging device 39, such as an MOS device or CCD, isprovided adjacent the waveguides 34 coupled to the optical elements 32along the X and Y receive sides of the touch screen 14.

Referring to FIG. 3A, a multi-layer flexible waveguide substrate 28according to another embodiment of the invention is shown. In thisembodiment, the two layers of optical elements 32 are provided along oneside of the substrate 28. A first or bottom layer of optical elements 32a are provided at spaced intervals. A second layer of optical elements32 b are provided above the first layer. The second layer of opticalelements 32 b are interleaved between the those of the first layer.Similar to the embodiment described above, the waveguides 34 of theoptical elements 32 a and 32 b are grouped together in a highway 36which runs the length of the substrate 28.

Referring to FIG. 3B, a diagram illustrating the multi-layer flexiblesubstrate of FIG. 3A is shown. In the figure, the first layer of lenses32 a and the second layer of lenses 32 b are shown around the peripheryof touch screen 14. One advantage of the interleaved, two layeredstructure of FIG. 3A, is that it provides greater resolution for a givendimension of the optical elements 32.

As illustrated in FIG. 3C for example, the optical elements 32 have awidth of approximately 1 mm each. As such, the distance between theinterleaved optical elements 32 is approximately ½. The touch screen 14of FIG. 3B therefore has the ability to resolve interrupts of ½ orgreater. In contrast, a substrate 28 with only a single layer of opticalelements of approximately 1 mm in width, would have a resolution of only1 mm, The aforementioned dimensions are exemplary and should not beconstrued as limiting the invention in anyway. Finer or courserresolution can be achieved by using smaller or larger optical elements32 respectively.

Referring to FIG. 4A, a cross section of a folded 40 waveguide substrateused with a touch screen 14 according to another embodiment is shown.This embodiment, referred to as a “folded” waveguide, is described inthe aforementioned co-pending parent application. In this embodiment,the substrate 40 includes a flat internally reflective surface 42 thatallows the waveguides to be folded on to the side surface of thesubstrate 40. With the waveguides on the side surface, the width of thesubstrate 28 can be reduced. Like the other embodiments described above,the substrate 40 of FIG. 4A is fabricated and then cut from sheet 30 asdescribed herein.

Referring to FIG. 4B, a partial perspective view of the folded waveguide40 provided around a touch screen display 14 is shown. As illustrated,the optical elements 32 of the waveguide are provide along the top sideof the waveguide 40 around the periphery of the touch screen 14. Theindividual waveguides 34 are folded and are grouped in highways 36 alongthe side surface of the substrate 40. A light source 38 and imagingdevice 39 are shown adjacent the where the waveguides 34 terminate.

FIG. 4C, a cross section of a folded 40 waveguide substrate used with atouch screen 14 according to another embodiment is shown. Thisembodiment, also referred to as a “folded” waveguide, is described inthe aforementioned co-pending parent application. In this embodiment,the substrate 40 includes a curved internally reflective surface 42 thatallows the waveguides to be folded on to the side surface of thesubstrate 40. With the waveguides on the side surface, the width of thesubstrate 28 can be reduced. Like the other embodiments described above,the substrate 40 of FIG. 4C is fabricated and then cut from sheet 30 asdescribed herein.

Referring to FIG. 5, a flow diagram 50 illustrating the manufacturingsteps for fabricating the various embodiments of the waveguidesubstrates 28, 40 and 90 of the present invention is shown. In aninitial step (box 52), a low N optical material is coated over the sheet30. In various embodiments, the sheet 30 is made from flexible, butmechanically strong, material, such as plastic or polycarbonate. Thesheet can be either transparent or opaque. According to variousembodiments, any low N optically transparent material can be used. Inthe next step (box 54), a high N optically transparent material iscoated over the sheet 30. The optical elements 32 and waveguides 34 arethen formed in the high N optically transparent material usingphotolithography (box 56). Specifically, the high N layer is masked andpatterned to form the optical elements 32 and the waveguides 34. Anotherlow N optical layer is then formed over the patterned high N opticallayer (box 58). The high N material is thus sandwiched between the twolower N layers, creating an internally reflective surfaces wherever thehigh N and low N materials are in contact. As a result, the opticalelements 32 and waveguides 34 are created. In a final step, thesubstrates 28 are cut from the sheet 30 (box 60). The multi-layerflexible substrates of FIGS. 3A-3C as well as the substrate of may befabricated using essentially the same technique. After the first layerof optical elements 32 and waveguides 34 are formed, an intermediatelayer is formed over the second N layer. The aforementioned processdetailed in steps 52-58 is then repeated.

Referring to FIG. 6, a diagram illustrating the manufacture of waveguidesubstrates according to another embodiment of the invention. With thisembodiment, the substrates 28 or 40 are fabricated by passing acontinuous strip of base material through a succession of processingstations. Initially at station 60, a spool of the base material 62 isprovided. The base material 62 is fed to a processing station 64 wherethe first low N layer is applied. As the base material rotates aroundthe station 64, a UV curing device 65 cures the first N layer. Atstation 66, the second high N layer is applied and cured in a similarmanner. At station 68, a layer of photo-resist is applied and cured overthe second layer. A patterning mask is them applied at station 70. Thepattern defines the optical elements 32 and the waveguides 34.Thereafter, portions of the second high N layer that do not form theoptical elements 32 and waveguides 34 are etched or removed at station72. The third low N layer is then applied at station 74. The processstrip of waveguide substrates 28 or 40 is then spooled at station 80. Inone embodiment, the circumference of each processing station issubstantially the same as the length of each waveguide substrate 28 or40. In this manner, a spool of base material can be fabricated into aplurality of serial waveguide substrates 28 or 40, each of equal length.The spool is later cut at periodic intervals equal to the length of eachsubstrate to singulate the individual substrates

Referring to FIGS. 7A and 7B, a diagram illustrating another flexiblewaveguide according to the present invention is shown. The flexiblewaveguide substrate 90 includes a plurality of optical elements 32 andcorresponding waveguides 34 arranged in two waveguide highways 36 a and36 b. The waveguide substrate 90 also includes a fold 92 separating thehighways 36 a and 36 b. The waveguide highway 36 a and 36 b extend ontothe corresponding sides of the fold 92. After the individual substrateis fabricated and singulated (in any one of the ways described above)the waveguide 90 may be folded along the fold. As illustrated in FIG.7B, the two sides of the flexible waveguide 90 are shown positioned atapproximate right angles with respect to one another with the two sidesof the fold extend outward. This arrangement makes it convenient for alight source and/or an imaging device (both not shown) to be positionedclose too or adjacent to the individual waveguides 34 of the highways 36a and 36 b on either side of the fold 92.

Although the foregoing invention has been described in some detail forpurposes of clarity of understanding, it will be apparent that certainchanges and modifications may be practiced within the scope of theappended claims. Therefore, the described embodiments should be taken asillustrative and not restrictive, and the invention should not belimited to the details given herein but should be defined by thefollowing claims and their full scope of equivalents.

1. An apparatus, comprising; a flexible base material; a first opticallayer formed on the flexible base material, the first opticallytransparent layer having a first index of refraction value; a secondoptical layer formed on the first optical layer, the second opticallayer being patterned to form a plurality of optical elements andwaveguides respectively, the second optical layer having a second indexof refraction value higher than the first index of refraction value; athird optical layer formed on the second optical layer, the thirdoptical layer having a third index of refraction value lower than thesecond index of refraction value, the base material and first, secondand third optical layers forming a flexible waveguide substrate, and theapparatus further comprising a light based touch screen having theflexible waveguide substrate formed substantially around the perimeterof the touch screen, a first sub-set of the plurality of opticalelements of the flexible waveguide substrate being configured to providelight adjacent to the light based touch screen and a second sub-set ofoptical elements of the flexible waveguide substrate configured todetect data inputs made to the light based touch screen.
 2. Theapparatus of claim 1, wherein the first index or refraction value andthe third index of refraction value are substantially the same.
 3. Theapparatus of claim 1, wherein the flexible base material comprises oneof the following materials: plastic or polycarbonate.
 4. The apparatusof claim 1, wherein the second optical layer is further patterned toform a plurality of internally reflective surfaces between the pluralityof optical elements and waveguides respectively.
 5. The apparatus ofclaim 4, wherein the plurality of optical elements are formed on a firstsurface of the waveguide substrate and the plurality of waveguides areformed on second surface of the waveguide substrate, wherein the firstsurface and the second surface are substantially at right angles withrespect to one another.
 6. The apparatus of claim 1, wherein the opticalelements comprise one of the following types of optical elements:lenses, diffraction gratings, filters, bragg gratings, or couplinghorns.
 7. The apparatus of claim 1, wherein the plurality of opticalelements patterned in the second optical layer are arranged in multipleslayers.
 8. The apparatus of claim 7, wherein the plurality of opticalelements in the multiples layers are interleaved.
 9. The apparatus ofclaim 1, further comprising a light source optically coupled to thewaveguides associated with the first sub-set of optical elementsrespectively.
 10. The apparatus of claim 9, further comprising animaging device optically coupled to the waveguides associated with thesecond sub-set of optical elements respectively.
 11. An apparatus,comprising a flexible base material, the flexible base material having aplurality of flexible waveguide substrates formed thereon, each of theflexible waveguide substrates comprising: a first optical layer formedon the flexible base material, the first optically transparent layerhaving a first index of refraction value; a second optical layer formedon the first optical layer, the second optical layer being patterned toform a plurality of optical elements and waveguides respectively, thesecond optical layer having a second index of refraction value higherthan the first index of refraction value; a third optical layer formedon the second optical layer, the third optical layer having a thirdindex of refraction value lower than the second index of refractionvalue, and the apparatus further comprising a light based touch screenhaving the plurality of flexible waveguide substrates formed in apattern substantially around the perimeter of the touch screen, a firstsub-set of the plurality of optical elements of the flexible waveguidesubstrate being configured to provide light adjacent to the light basedtouch screen and a second sub-set of optical elements of the flexiblewaveguide substrate configured to detect data inputs made to the lightbased touch screen.
 12. The apparatus of claim 11, wherein the pluralityof substrates are arranged in parallel strips on the flexible basematerial.
 13. The apparatus of claim 11, wherein the flexible basematerial is a continuous strip and the flexible waveguides substratesare serially formed on the flexible base material.
 14. The apparatus ofclaim 11, wherein the waveguide substrates comprise a plurality opticalelements and waveguides.
 15. The apparatus of claim 14, wherein theoptical elements are arranged in multiple layers and the opticalelements are interleaved.
 16. The apparatus of claim 14, wherein theoptical elements comprise one of the following types of opticalelements: lenses, diffraction gratings, filters, bragg gratings, orcoupling horns.
 17. The apparatus of claim 11, wherein the flexiblewaveguide substrates are further patterned to form a plurality ofinternally reflective surfaces between the plurality of optical elementsand waveguides respectively.
 18. The apparatus of claim 17, wherein theplurality of optical elements are formed on a first surface of theflexible waveguide substrate and the plurality of waveguides are formedon second surface of the flexible waveguide substrate, wherein the firstsurface and the second surface are substantially at right angles withrespect to one another.
 19. A method comprising: providing a firstoptical material over a flexible base material, the first opticalmaterial having a first index of refraction value; providing a secondoptical layer on the first optical layer, the second optical layerhaving a second index of refraction value higher than the first index ofrefraction value; patterning the second optical layer to form aplurality of optical elements and waveguides respectively; providing athird optical layer formed on the second optical layer, the thirdoptical layer having a third index of refraction value lower than thesecond index of refraction value, the base material and first, secondand third optical layers forming a flexible waveguide substrate, andforming the plurality of flexible waveguide substrates in a patternsubstantially around the perimeter of a light based touch screen, afirst sub-set of the plurality of optical elements of the flexiblewaveguide substrate being configured to provide light adjacent to thelight based touch screen and a second sub-set of optical elements of theflexible waveguide substrate configured to detect data inputs made tothe light based touch screen.
 20. The method of claim 19, furthercomprising forming a plurality of the flexible waveguide substrates onthe base material.
 21. The method of claim 20, wherein the forming theplurality of flexible waveguide substrates further comprises: providingthe first, the second and the third optical layers in side-by-sidestrips on the base material; and cutting the base material to singulatethe individual flexible waveguide substrates.
 22. The method of claim21, wherein forming the plurality of flexible waveguide substratesfurther comprises: providing the first, second and third optical layersserially at spaced intervals on a continuous strip of the flexible basematerial; and cutting the continuous flexible base material at thespaced intervals to singulate the individual waveguide substrates.